We have collected a variety of data, ranging from MRI measurements of tumor (fibroid) volumes over time (up to 4 time points) to gene expression microarray data obtained on tumors from women who opted for surgery. We examined tumor growth in relation to patient characteristics (ethnicity, age, and number of fibroids) and tumor characteristics (size and position in the uterus). In all there were 72 women in the study contributing a total of 262 tumors for the analysis of growth. Volumes of all 262 tumors were measured at least at two time points. Our analysis of this data suggests that there was a significant variability in average tumor growth both, both between and within women. Interestingly, within woman variation was twice that of between women. Blacks and whites had different patterns of fibroid growth depending on age. Among young women (<35), fibroid growth rate did not vary by ethnicity. However, growth rates declined with age for whites but not blacks. The odds of a tumor growing more than 20% in six months also decreased with age for whites but not for blacks. Growth rates were not influenced by tumor size, location, BMI, or parity. Spontaneous regression of fibroids occurs. Fibroids from the same woman grow at different rates, despite a uniform hormonal milieu. Size does not predict growth rate. Age-related differences in fibroid growth rates between blacks and whites may contribute to the higher symptom burden for black women.